Right!.. but
IMO Given a situation where an amplifier is operating in bridged mode, musically it will be discernible as a harsh top end, and muddy lows. Trying to calculate damping factor is not logarithmic with the impedance so.., don't get clinical about it.

 

As stated the amp must control the speaker, the speaker must also control the speaker...

The speaker's performance is typically dominant from its T/S parameters, BUT that does not mean the performance of the amp is unimportant to THE SYSTEM (or closed electrical circuit)

We are dealing with a "DC system" but the end product is music and an "AC system" the speakers resistance is what most folks worry about but the performance of the speaker involves frequency dependant inductive/ capacitive reactance and this makes for a complex waveform from the electrical phase angle point of view. As to how this ends up sounding is the end question... does the amplifiers grip on all resistive, capacitive and inductive issues keep the electrical signal to the speaker looking like the trace from the preamp? And if it doesn't how do these frequency dependant phase angles (or deviations from linearity) affect sound? The better the amplifier is engineered the closer the waveforms should be to each other (yet this isn't a rule either as exceptions happen (for instance...) the tube amps that sound good but shouldn't as their specs into complex impedances SUCK). Can you hear the deviation from the original signal or is it more of an impression you get (out comes the audiopeak mumbo jumbo)? IMO this is why there is a difference in amplifier sound (other than the manufacturers EQ in their design) it is not that the amplifiers sound different inherently they just end up performing differently into the same load. Not a terribly concrete thing and a difficult precipice to stand on electrically.

 

And back to my earlier comment... so if they ALL sound the same then the specifications we use (ALL OF THEM) mean nothing to the SQ orientated purchaser. You're stating, and I am not disagreeing, that it may all be sonic shinola. The specifications indicate a performance based design, but its electrical performance we are designing to not sonic performance necessarily. A poorly built amp should not out perform a well built amp ... ever... yet does it matter from a sonic point of view? This discussion has jumped into an electrical nuts and bolts discussion and has ignored alphas interesting comment and I commend and condemn at the same time as it destroys the electrical engineers world and the SQ consumers world (nothing matters). It is my philosophical contention that everything matters and yet nothing does (hence why I named my business Voodophile). I do think the measurements we use are pretty meaningless as a thermometer of sonic performance, but they are good thermometers of electrical performance. So the better the amps are designed they better they should perform as a straight wire with gain.
The discussion on EMF and BEMF are essential to this and point out this IS NOT a V=IR question.
From a EE point of view how can't they sound different if their specs are different?

 

Amplifiers do not sound the same, and specifications will never tell you what the result will be with YOUR equipment, rather only with TESTING equipment.
And you are right John, specifications for the MOST part are meaningless at best, especially for the consumer who gets into them more so than his target of obtaining quality sound for his $. I don't listen to specification sheets, I listen to music a much more complex set of signals than a test tone, through a loudspeaker which is a reactive load, not a scope or resistor .